Inkjet printers generally employ one or more printheads, also referred to as pens, to deposit ink on a print medium. The deposited ink forms an image on the print medium, details of the image being controlled by print data. Generally, the formed image may contain one or both of graphic content (e.g., drawings, graphs, photographs, etc.) and text content (i.e., letters and words).
In particular, the print data instructs the printhead when to deposit the ink, often in the form of small droplets, as a location or position of the printhead moves relative to the print medium. In various inkjet printer configurations, one or more of several methods that eject or expel ink from a nozzle or nozzles of the printhead may provide ink deposition by the printhead under the control of the print data. For example, in thermal inkjet printing, discrete droplets of ink are expelled from the printhead by passing a current through a resistive heating element in a chamber behind the nozzle. The current causes the resistive heating element to heat up and substantially vaporize a portion of the ink in direct contact with or in a vicinity of the resistive heating element. The vaporized ink forms an expanding bubble that, in turn, forces the ink in front of the bubble out of the chamber through the nozzle.
In some situations, residual ink may deposit one or both of on and around various electrical contacts of the printhead resulting in the formation of a short circuit. For example, the residual ink may deposit on electrodes that supply current to the resistive heating element. This residual ink deposition may short circuit the resistive heating element within the printhead, for example.
Attempts to address ink shorts and related short circuits in inkjet printer printheads have typically been focused on performing short circuit monitoring and detection when the inkjet printer is not printing. For example, an ink short detection algorithm may be run to detect ink shorts one or both of in between passes of the printhead across the print medium and in spaces between pages being printed. In many examples, a central processing unit (CPU) of the inkjet printer is responsible for running the ink short detection algorithm. For example, Espasa et al., U.S. Patent Application Publication No. 2007/0046712 A1 describe detecting ink shorts based on a page-by-page estimate of current consumption. According to Espasa et al., the ink short detection occurs after a page is printed but before printing begins for the next page.
However, in some situations there may be substantially no break in the printing (e.g., between passes or pages) that would allow time to perform short circuit detection. For example, in the case of commercial inkjet printers there may be no time between pages to perform the ink short detection algorithm. In other cases, the image may be substantially continuous and without page breaks for long periods of time. Moreover, in many cases the CPU is simply too busy controlling the printing process to also be responsible for monitoring and detecting potential printhead short circuits.
Certain embodiments have other features that are one of in addition to and in lieu of the features illustrated in the above-referenced figures. These and other features are detailed below with reference to the preceding drawings.